cmd: mvebu/bubt: Fix cmd main return value on error

Negative return value from cmd main function cause U-Boot to print criplic
error message: exit not allowed from main input shell.

Set return value on error to 1.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>
1 file changed